Solved !!! 💡
Cleanliness is next to Godliness !!
A small piece of congealed oil was trapped in the corner of the brass piston ring stop, keeping the ring slightly open and causing a tight spot when the crank was turned.
thanks for the advice it put me well on the way to the solution , although it does indicate that the bores are not perfectly cylindrical may need a rebore in the near future
Kind regards and thanks again for your contributions
